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    SubjectRe: sendmsg() arguments
    Date
    Hello!

    > In Linux 2.0.x and other systems sendmsg() in its second argument msg
    > allows msg->msg_namelen to contain nonsense if msg->msg_name is NULL (what
    > kinda makes sense -- NULL in msg->msg_name means that there is no address
    > involved, so its size is meaningless). However 2.2.x checks msg->msg_namelen
    > instead -- if it's nonzero, msg->msg_name is considered to be an address
    > even if it's NULL (and therefore error is returned). Why?

    Because I consider this as the only correct way.

    sendmsg() behaviour is not prescribed by any standards
    and this way is preferred, because:

    - it is error prone: bad msg_name and msg_namelen!=0 is
    usual application bug, showing malloc failure or memory corruption.
    - it saves one statement if (name==NULL) namelen=0

    BTW some time ago recvfrom() behaved in the same manner,
    but broken way appeared to be described as valid in UNIX98,
    so that it was changed.

    Alexey Kuznetsov

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